diff --git a/src/cmd/compile/internal/gc/inl_test.go b/src/cmd/compile/internal/gc/inl_test.go
index 1ad6ca34215..0dfd252372f 100644
--- a/src/cmd/compile/internal/gc/inl_test.go
+++ b/src/cmd/compile/internal/gc/inl_test.go
@@ -133,14 +133,11 @@ func TestIntendedInlining(t *testing.T) {
 			"Value.pointer",
 			"add",
 			"align",
+			"flag.mustBe",
+			"flag.mustBeAssignable",
+			"flag.mustBeExported",
 			"flag.kind",
 			"flag.ro",
-
-			// TODO: these use panic, which gets their budgets
-			// slightly over the limit
-			// "flag.mustBe",
-			// "flag.mustBeAssignable",
-			// "flag.mustBeExported",
 		},
 		"regexp": {
 			"(*bitState).push",
diff --git a/src/reflect/value.go b/src/reflect/value.go
index 372b7a6dc80..5951b18b8c9 100644
--- a/src/reflect/value.go
+++ b/src/reflect/value.go
@@ -203,7 +203,8 @@ type nonEmptyInterface struct {
 // v.flag.mustBe(Bool), which will only bother to copy the
 // single important word for the receiver.
 func (f flag) mustBe(expected Kind) {
-	if f.kind() != expected {
+	// TODO(mvdan): use f.kind() again once mid-stack inlining gets better
+	if Kind(f&flagKindMask) != expected {
 		panic(&ValueError{methodName(), f.kind()})
 	}
 }
@@ -211,8 +212,14 @@ func (f flag) mustBe(expected Kind) {
 // mustBeExported panics if f records that the value was obtained using
 // an unexported field.
 func (f flag) mustBeExported() {
+	if f == 0 || f&flagRO != 0 {
+		f.mustBeExportedSlow()
+	}
+}
+
+func (f flag) mustBeExportedSlow() {
 	if f == 0 {
-		panic(&ValueError{methodName(), 0})
+		panic(&ValueError{methodName(), Invalid})
 	}
 	if f&flagRO != 0 {
 		panic("reflect: " + methodName() + " using value obtained using unexported field")
@@ -223,6 +230,12 @@ func (f flag) mustBeExported() {
 // which is to say that either it was obtained using an unexported field
 // or it is not addressable.
 func (f flag) mustBeAssignable() {
+	if f&flagRO != 0 || f&flagAddr == 0 {
+		f.mustBeAssignableSlow()
+	}
+}
+
+func (f flag) mustBeAssignableSlow() {
 	if f == 0 {
 		panic(&ValueError{methodName(), Invalid})
 	}
@@ -981,7 +994,7 @@ func (v Value) Interface() (i interface{}) {
 
 func valueInterface(v Value, safe bool) interface{} {
 	if v.flag == 0 {
-		panic(&ValueError{"reflect.Value.Interface", 0})
+		panic(&ValueError{"reflect.Value.Interface", Invalid})
 	}
 	if safe && v.flag&flagRO != 0 {
 		// Do not allow access to unexported values via Interface,